Title: The diffusion of lethal and non-lethal violence in gang networks
Name: Andrew V. Papachristos
Yale University
Year: 2010, 2011
Type: Research Grant

Gangs conjure a general sense of fear among the public and policymakers alike. In part, this fear stems from the nature of gang activities, which, as the term street gang suggests, most often occur on the street or other public spaces. Whats more, gang violence is more likely to involve the use of firearms and involve a greater number of participants. Drive-by shootings, for example, harm not just those struck by bullets, but also other residents of the community who fear for their familys safety, lock their doors, or otherwise withdraw from community life.

In truth, however, the majority of gang violence is far from random. Gang violence most often occurs among gang members themselves, the result of prior intergroup conflict resulting from disputes over status, honor, or respect. Criminologists and sociologists have long known that violence tends to concentrate within certain populations and geographic locations, but a growing body of research finds that gun and gang violence is even more severely concentrated within social networks. This HFG funded research explored the role that social networks play in the decidedly non-random nature of gang violence in two U.S. cities: Chicago and Boston. In particular, this project analyzed the ways in which gang networks contribute to the spread of violence both within a population of gangs and gang members as well as outwards into the general public. The main findings of this research underscore the importance of networks in understanding the diffusion of gun and gang violence.

This projects main findings can be summarized as follows:

  1. Fatal and Non-Fatal Gun Violence is Severely Concentrated within Small Social Networks.

    One of the most significant findings from this research is just how concentrated gun violence is within social networks. For example, in a study of one high-crime Boston community, this research found that 85 percent of all fatal and non-fatal gunshot injuries occurred within a network comprising just 763 individuals--less than 5 percent of the community's totally population. Moreover, this study demonstrated the gunshot victims could be located with fairly high accuracy within such networks; and network maps can provide excellent visualizations of such risk within a population.

  2. Exposure to Gun Violence Matters - A Lot

    Not only does gun violence concentrate within social networks, but exposure to violence in one's social network matters in predicting subsequent victimization; in fact, it matters more than more traditional individual and neighborhood-level risk factors. Estimates from this research suggest that the closer one is to a gunshot victim, the higher ones own probability of getting shot. More precisely, estimates from the Boston study suggest that each handshake away one is from a gunshot victim reduces ones probability of being a victim by approximately 25 percent. The effect is greater for gang members, in large part because being in a gang sharply determines the contours of ones network. Gang networks, then, play an important role in shaping how risk is distributed within social networks, especially as it relates to exposure to gun violence.

  3. The Corner and the Crew: The Importance of Geographic Space and Gang Networks

    The results from a comparative study of gang violence in Chicago and Boston found that one of the most important factors influencing observed patterns of gang violenceliterally, who shoots whomare larger networks of conflict and violence between gangs. Gangs are not myopic, and gangs (especially in Chicago) have long organizational memories. In both Chicago and Boston one of the most robust predictors of gang violence is the network structure of any gangs past conflicts and battles. Put another way, understanding a gangs prior pattern of conflict and violence goes far in predicting whom the gang will engage next. Such gang networks are influenced by geographic space as well. But the most important drivers of gang violence appear to be the ways in which reciprocity and status-seeking violence unfold within such conflict networks. In fact, in both Chicago and Boston individual incidents of violence between gangs string together to form a social network that appears to exert enduring effects on subsequent acts of violence.


Papachristos, A.V., A.A. Braga, and D. Hureau, Social Networks and the Risk of Gunshot Injury. Journal of Urban Health, 2012. 89(6): p. 992-1003.

Papachristos, A.V., D.M. Hureau, and A.A. Braga, The Corner and the Crew: The Influence of Geography and Social Networks on Gang Violence. American Sociological Review, 2013. 78(3): p. 417-447.